Hidden Sister
by FrostHitsugaya19
Summary: Have you ever thought about our dear Dazai Osamu's family? This is but a fanfic about his pretty hidden secret. The secret that he, himself, doesn't even know as well. How and what will his sister do for him to remember who she is? What happened in the past? Who is she? "Mark my words: there are a lot more hidden secrets that you don't know." Dazai Zennon
1. AN

**DISCLAIMER: I DO NOT OWN BUNGO STRAY DOGS**

This is a work of fiction. Names, characters, business, companies, places, events, and incidents are all products of the author's imagination. Any resemblance to actual persons, living or dead, or actual places and events is purely coincidental.

This is an original fanfic of FrostHitsugaya19.

All rights reserved.

ENJOY~

Vote and comment! ^-^

|Hitsu-kun|


	2. Prologue

**DISCLAIMER: I DO NOT OWN BUNGOU STRAY DOGS**

 **PROLOGUE**

 _Death is an unusual thing to think about._

Well, that is if you're a man named Dazai Osamu.

He is so honest, so eager, so energetic, and so crazy in killing himself, yet never succeeds. Why? From what I know, he wants to fill in that little black hole forming in his heart... that unending loneliness...

Though, I quite don't get him. I'm still amazed by how he's doing it.

Last time I checked, he happily jumped from a rooftop as if taking a dive in a pool but then got stuck on a tree branch.

Then, months ago, he was literally swimming near piranhas in a zoo, and for death's sake, he won't die! He was saved by a man, who thought Osamu doesn't want to die.

I wonder... are the grim reapers not tired, annoyed, and irritated of his acts?

Suddenly, his vision has shifted from suiciding alone without suffering, to suiciding with a beautiful girl, who wants to double suicide with him.

He is an absolute masterpiece.

While these thoughts filled my head as I was eating my breakfast and lunch for this day, I walked down the streets with my right hand shoved into my jacket's pocket.

My burger smells and tastes good that I didn't notice where my feet led me to.

"Hey," greeted the familiar voice. I turned around, gulping a small part from my burger.

Oh, it's the chibi.

"What are you doing standing in my way?" he asked. I just yawned, then chewed on my burger. He is so dominating as ever. I saw his expressions changed.

Oh-ho. Ranpo's so cute with him being childish.

I continued eating, minding nothing of his change of aura. "You see chibi Ranpo, you can just say 'please'," I teased.

Of course, he wasn't happy. I mean, why would the great detective of the Armed Detective Agency say please to a complete stranger? But, then again, I said his name, making him open his bold green eyes, and bored his eyes into mine.

"Did you just say CHIBI Ranpo?" he asked. "Chibi?"

He's mad.

It suddenly hit me. I looked at my back and saw where I was standing, the stairs to the Armed Detective office. I am a total airhead for not noticing.

I turned to my left, stepped aside and continued walking. I had a glimpse of the chibi looking at me as if asking me 'why'd I go', but I didn't bother to look back.

The Armed Detective Agency or ADA, according to my researches, consists of a bunch of mostly ability users, who are violent lions that the Military Police has difficulty in taming. They half-ly solve crimes and half-ly deal with the port mafia.

What geeks me out is their director, Fukuzawa Yukichi, and the Port Mafia's boss, Mori Ougai, have a great past. They continued battling head on, yet in rare occasions helped each other.

I finished my burger and tossed it in a nearby trash can. It wobbled first before it fell right in.

I bought myself a bottled water and did the same.

"Ahhh~ That was great! I could live my life with just burgers," I lazily said. I felt the opportunity to sit and to relax on a bench, just near the trash can where I tossed the bottle.

I saw the tiger talking with the Doppo Poet, and beside them stands the suicidal maniac, cutting lines between the two, as much as possible, and Kunikida just scolds him because of his puns. The tiger and the poet are eating burgers while the nullifier doesn't.

I smiled.

I reached for my scarf and lifted it up, reaching until my nose. Now, I can only see fragments through my hazelnut colored eyes since part of my bangs has scattered through my face. I, then, pushed my hands in my jacket's pockets, stretching a little.

"Heya, Kunikida-kun, Kunikida-kun," called Dazai, childishly.

"What?!" the answer.

"Did you know those seeds that are planted in the bun of a burger would soon grow as a bun tree, once water and sunlight reach the bun for over an hour?" a widely explained trivia by Osamu.

"Pfffttt..." I reacted in a low voice.

"I see... that's why they make those burger stands! Also, that is why they deliver the buns in a truck and store in a place away from the both!" realized Kunikida in a serious tone, writing every word Dazai said in his infamous notebook.

He took it seriously! O M G! I stopped myself from the urge of laughing by gritting my teeth as hard as I could.

"Tehee~ It was a joke!" confessed Osamu.

I heard a loud and angry yell, followed by a series of I-cannot-comprehend-because-of-its-speed lecture, all coming out of the poet's mouth.

I saw my brother laughing and the tiger calming his senior down.

I faintly smiled, that's for the third time this week. That should have been a record for me.

I didn't bother looking back at the three. I yawned and went on with my plan: falling asleep.

It was a nice thing, the falling asleep part where I get out of reality and be swarmed in an another dimension, just meant for myself and my imaginations.

But, someone killed it.

SOMEONE disrupted my sleep.

I quickly shoved my left hand in front if me, pushing whoever that person is, away from my beautiful face.

"Who was that?!" I madly asked, opening my eyes.

And right in front of me, inches away from my face, an idiot bandaged-mummy man sits. He is looking at me with that stupid smiling face and closed eyes.

I sighed inwardly when I realized it was just Osamu. Well, because if it was some other human, I would definitely send them to hell.

I hate people who disrupt my sleep.

I rolled my eyes. "Who the hell are you?" I acted with an annoying voice.

Osamu stood up and started dancing while saying, "You know~ Young lady~ Do you want to do double suicide with me?~" He ended up stretching his hands in front of me and kneeling as if asking me for a dance.

I looked at him with my dead flat bored look.

"Kill yourself," I noted.

Roses started dancing around him-wait, what? He gave me a flirty smile and held both of my hands, only receiving a smack from Kunikida.

But his goal didn't waver. He continued, "That's that! Yes! I would love to die~ However," He stood up and posed in a thinking position. His aura changed to a serious one as if crying and pleading. "I would want to die with you! Such an act is only as beautiful as two beautiful humans die together! A perfect double suicide!"

Again, he had received a smack.

He was about to be given another lecture when I cut in.

"Alright then, I would suicide with you," I promised with a cunning smile. My scarf's already down and my bangs have been blown at my left by the wind.

It's as if the whole world stopped.

The people walking stopped and looked at us. Kunikida froze and Nakajima looked like heaven and hell has forsaken him. Osamu, on the other hand, stopped moving as well, but his smile retains.


	3. Chapter 1

**DISCLAIMER: I DO NOT OWN BUNGOU STRAY DOGS**

ooo

 **CHAPTER 1: Predictions**

ooo

Seriously, if death would be happy to get me, I AM PLEADING! GET ME NOW!

Osamu has this bright, shiny, and puppy eyes twinkling in front of me while holding my hands. Kunikida face palmed, unable to finish his burger, and Nakajima looked worried, glancing at me, then to Osamu.

I sighed.

"I would if you die, and I survive," I said with a smile. The three silenced, all looking at me.

I stood up, slipping my hands away from Osamu's, and started to walk away. Clearly, those three forgot what they came here for or in actuality, Osamu knows that I've been following him.

He's not dumb.

But, he is so dumb for believing what the news has said.

I smirked and looked back at them. Osamu's crying like a baby on a bench, being comforted by Nakajima. Nakajima tries his best to calm down the mummy from stopping him in making a scene. Kunikida threw the burger wrapper in the nearby trash can and fixed his glasses.

I looked back on the road and pulled my scarf up.

I can't wait to tell him that I am his sister!

ooo

As always, I need to walk through how many alleys before going back straight at the villa. But, before I could even turn another alley, someone blocked my way.

It's so dark here, but on how the wind goes, someone taller than me stands in my way. I hear the muffle of a long coat.

In my whole life, there are only three people who can stand in my way without making any heeltaps, who are tall enough to wear a long coat, and who knows me.

That person's either Mitsuho Akio or Midori Nikki or Al Rexia.

But, considering the smell of this person, he is...

"Dazai Osamu," I called.

He clapped. He slowly started walking towards me, and I can't help but move backward. "You know my name," he stated with a smile, still clapping.

Now, I know the feeling of those people that crossed with Osamu before. Got chills when he talks, got chills when he smiles, got chills when he suddenly looks at you.

I know what he's going to do next because I can hear his movements. His right hand's already out of his pocket and he's waiting for me to reach the end of this alley. He's going to pin me to the wall by his right hand.

I wall jumped, from left to right, repeatedly. I reached the peak of the wall and started jumping through roofs like a ninja. I looked back and my eyes widened.

HE'S JUST A RULER AWAY FROM ME!

I looked back and quickly sped up, but no matter how hard I try, he can still pick up with my speed.

"What do you want?!" I shouted. The air pressure makes it hard to speak. Even if it's so windy, I can still perfectly and accurately make my jumps. The good thing is my scarf's kind of glued to my jacket.

"You were good earlier!" he commented, avoiding my question. "How did you know what I'll do next?!" he added.

"I've watched a ton of movies to know your next moves!" I answered.

"Really? Because I don't believe you," he said. Chills went down my spine as I hear him whisper in my ears. I lost my balance and fell.

Uwah... That was creepy...

I was in an 18 story tall building and I can hear a crowd underneath my death bed. Suddenly, swept by a large, cold, and fast wind, someone caught me from falling.

Still shocked by what just happened, I blinked a thousand times before realizing that I am already in the tiger's arms. He's carrying me the bridal style. His feet changed, but his looks remained so I complemented the director of ADA inwardly for his great ability.

I closed my eyes.

We landed in a nearby flowing river where Kunikida's waiting. How do I know? The scent of the water and Kunikida, as well as the sound of the river and Nakajima's gentle landing feet.

"Is she dead?" asked Kunikida.

"Passed out, I think," guessed Nakajima.

I sensed another man landing beside us. Of course, it's Dazai Osamu.

"Bring her down and leave us," he ordered. Before the two could even ask why I quickly jump out of the tiger's hands and make my distance.

"You bastard," I hissed with a smiling face, boring my eyes into his.

We both have our hands in our pockets. He is his trench coat and mine is my jacket.

"You bitch," he answered with his trademark and evil smirk.

I felt my throat drying up. I gulped nervously.

ooo

"SHE IS LATE!" shouted by Axel Rexia, walking around and around the huge living room.

Al, who's the first-born, laughed.

"C'mon, Ax. Nothing bad's gonna happen to her, right, Ace?" said Al Rexia in his formal attire, ready for a formal date. He has his arms wrapped around his chest and legs crossed, showing dominance and power.

The second brother, Ace Rexia just nodded. He's currently playing with his 4-year-old, black cat with (right) blue and (left) green eyes. named Spade.

Al and Axel looked at each other, after looking at their introvert brother. Axel raised both hands asking without a word 'what's up with him?', and Al replied a shrug.

Suddenly, Ace stopped moving and quickly turned to his brothers, who just equally sensed him so they looked at him, as well.

"Why?" asked Al.

"Zennon. She's in trouble," a swift, low, cool, and understandable voice went out of Ace's rare speaking mouth.

Axel exploded and quickly ran at the door, to the outside world.

Al sighed at Axel's idiocy. "He even doesn't know the location," stated Al. He turned to Ace, who just yawned. "Where?"

Al's eyes glowed and a series of yellow words in lines, forming circles, appeared in front of it. After a while, it turned back to the way it was.

He just used his ability named 'Back to the Past', which allows him to see fragments in the past, future, and present to any person he wants to use it.

"She is located at a nearby river near xxxxx street," he answered.

"Ahhh... This is why being the eldest seems hard..." Al said, stretching his hands up, and walked to the door. Before he completely goes out, he advised his brother without looking, "Put up the wall."

With that, he went out.

ooo

Nakajima and Kunikida have left the place already, after reading the situation. I mean, what's the situation here?! They should've saved me!

"What's your name?" he asked, walking towards me. He has that scary eyes that's piercing you until the very end of your little atoms.

I was about to say my name when I remembered three things. One is that I would definitely be questioned a hundred times if I will say my real name. Second is his freaking unique gift to make others just throw out every tiny bit of information they had. Third, HE IS DAZAI OSAMU FOR HECK'S SAKE!

I was about to laugh so I lip bite. I couldn't hold it in and laugh frantically.

His serious face dropped. "Why? What?" he lazily asked, sighing. I hold my stomach as I was unable to stop my laughter. "What?" he repeated.

"Ahaha! W-wait! I need to- Ahahaha! Oh, my gash..." I continued saying whatever words in between my guffaw. I wiped my eyes as I smirked at him, getting my composure back.

"You are originally the dark Dazai Osamu of the Port Mafia," I started. He smiled at me with that dark brown eyes. "How couldn't you know me? I mean, you are great on every single thing except for being a human, which just contradicts what I just said. Anyways, you should be asking me another question other than that," I finished.

He laughed back at me.

"You brilliantly avoided," he noted. I moved towards him, he didn't move this time. "You don't need to act as well as if you don't know that I know you've been following me. As well as the fact that you erased every piece of your information," he added.

Now, we're a ruler away from each other, just like when we're ninja jumping.

"You're the only person that can put me down," I told him as I smile.

"And you're the only person that I don't understand," he said with a frown.

"Let's exchange information, then," I offered as I put my hand out, welcoming a handshake from him.

"Hehe~" He accepted it.

Green light came flashing in front of me as he uses his ability, 'No Longer Human'. I smirked at the close-up sight.

"You're not using any abilities?" he asked me with an eyebrow raised.

"Do I have one? What do you think?" I answered back. He gripped my hand as I was about to get away from it. I flinched. "What do you want?" I asked, again for the second time this day.

He looked down whilst his left hand was on his chin in a thinking position. "It just doesn't make any sense," he mumbled, but still I can hear it.

"The what?"

"I don't understand you," he told me as I just saw his smile was gone.

My smile faded away. "I also don't understand you," I responded back. He let my hand loose and put it back in his pockets. I did just the same thing. "Why? Did you really thought that all of your predictions will come true?" I asked, gaining attention from him.

He glared at me.

I stood up straight and cursed under my breath. That was a great killing intent. If looks could kill, I AM DEAD.

"What do you mean?" he retorted.

It's because I've already predicted that you're going to predict me so I predicted things the way you did and I just twist in my own predictions.

But, I didn't say that.

"Because you're Osamu, and I am Z. Hello and goodbye." That is how I introduced myself to my brother, after 17 years of no direct contact with him.

I know that they're already here. I predicted this happening after I lost my balance earlier.

A loud scream, that annoying voice, came from behind me. I raised my left hand, which was leveled by my shoulder and was facing the other direction against Osamu.

Axel came running towards us with his fist turned into, figuratively, stones, and my left hand just stopped him from punching Osamu, whom I believe has predicted this happening except the part of me stopping Axel.

I mean...if he stopped me in that alley, then that just means he was looking at me ever since I got in there because that alley was called the 'maze', which was a setup, created by an ability-user years ago for the elite families, to stop someone from following you.

The maze consists of pretty scary and sketchy alleys with traps all around the place. And only the elite families know where the traps are, so if you don't know, say your prayers and good luck.

Amazingly, mafia groups like the Port Mafia, the Guild, and the like have their own copies of the traps. They use the maze to lure in their guests (some informants, other drug dealers, whatever) and will, later on, leave them to die.

No police officer or government official has introduced 'the maze' in public since a few only knows it and these few people use it, too.

And I am sure that he knows that if I am using that way, then that just means that I am from a high estate family. And if I was already going down on that path, then it means two things: (1) I am going home, or (2) I am going to meet someone.

But knowing him and his port mafia years, which I still haven't completed my researches on, he knows that I am not there for meeting someone. He went down the alley and blocked me. Here go his two plans:

(1) If I got out there, he's gonna pin me before my 'friends' would come and get me. (2) If I can't get out of there, he'll straight me on with questions with his 'unique way of getting information'.

But I ruined his plans as I act along with his predictions. Though I know parts of his plans, I didn't predict of the fact that we're gonna ninja jump and the tiger would save me.

He is unpredictable so do I in his thoughts.

Axel stumbled on his feet as I sensed Al walking towards us. "Are you for some reasons, the same as me?" he confusedly asked.

I shrugged. "Probably."

"You called me Osamu."

"That's why I offered Z."

"Care for a drink next time, burger-eater-that-magically-leaves-no-finger-prints?"

"As long as Kunikida pays for it."

"Agreed."

"You know the time, I presume?"

"A park? Or forest? Just here?"

"Forest. It's wide to kill there."

"Learn how I predicted your predictions. It must've been easy now since you talked to me."

"I actually already know."

"Nice to meet you, Osamu."

"So do I, Z."

With that fast talk, he turned and walked out. I simply stared at him for a while.

I felt the sudden urge to pat myself on the back since I completely, FOR THE FIRST TIME IN YEARS, won to Osamu.

I looked up, seeing the clear sky, and smiled. You can now rest in peace, pops. I've finished your last wish.

ooo


End file.
